Which of the following ions would form (i) coloured and (ii) colourless complexes in water?
`Cu^(2+),Zn^(2+),Ti^(3+),Ti^(+4),Cd^(2+),Mn^(2+)`

Explanation

(i) `Ti^(3+), Cu^(2+(3d^(9)) and Mn^(2+)(4d^(10))` have unpaired electron (s). Thus they are coloured due to d-d transitio of electron according to CFT.
(ii) `Zn^(2+)(3d^(10)),Ti^(+4)(3d^(0)) and Cd^(2+)(4d^(10))` do not have unpaired electron(s). thus they do not under go d-d transition of electron accordigng to CFT and, therefore, are colourless.